Renal secretion of uric acid is impaired in a strain of chickens selected genetically for hyperuricemia and articular goat. Variations in dietary K, Na and Cl markedly influence plasma uric acid concentrations in normal chickens but not chickens of the hyperuricemic strain. The proposed investigation has two objectives: (1) To investigate binding of uric acid by protein fractions from kidneys from the hyperuricemic and control strains in an attempt to identify a protein fraction which may participate in uric acid transport, and (2) to investigate the role of mineral ions in uric acid transport. Binding of uric acid by kidney fractions will be assayed using a "wash in" ultrafiltration technique. Mineral interactions in uric acid secretion will be investigated in vivo using the Sperber technique to monitor renal secretion of uric acid and mineral ions in response to dietary variations of Na, K or Cl. Possible relationships between peritubular Na-K dependent ATPase and uric acid will be studied using enzyme assay and autoradiographic technique for localization of ATPase.